Nonlinear electrical behavior and dielectric properties of (Ca, Ta)-doped TiO2 ceramics

TiO2 ceramics doped with 2.5 mol% Ta and different concentrations of Ca were obtained by sintering at 1300degreesC. As a varistor material, the nonlinear electrical behavior and dielectric properties of these ceramics were investigated. The ceramics have nonlinear coefficients a in the range 2.0-5.5 and high relative dielectric constants. The effects of Ca on the density, nonlinear electrical behavior, resistivity and dielectric properties of the Ta-doped TiO2 ceramics were also studied. The sample doped with 0.75 mol% Ca and 2.5 mol% Ta exhibits the highest nonlinear coefficient and a comparatively lower relative dielectric constant. By analogy to a grain-boundary defect model, the nonlinear electrical behavior of the TiO2 system is explained. (C) 2002 Elsevier Science BY. All rights reserved.